Renewable fuse



G. R. TRUMBULL July 7, 1925.

RENEWABLE FUSE Filed Aug. 24, 1921 INVENTOR George R. Trumbull.

ATTORN S.

Patented July 7, 1925.

PATENT GEORGE n. TRUMBULL, or BANTAM, CONNECTICUT.

RENEWABLE FUSE.

Application filed August 24, 1921. Serial No. 495,036.

To all whom it may concern. I

Be it known that I, GEORGE E. TRUMBULL, a citizen of the United States of America, residing at Bantam, Connecticut, have in "entednew and useful Renewable Fuses, of which the following is a specification.

My invention relates to a renewable fuse. The usual renewable fuse consists of a body member having a passage for a renewable fuse link and means for connecting the link at the opposite ends of the fuse body. Suitable terminals, usually in the form of. ferrules or projecting blades, are providedto electrically connect with the fuse link and to conduct current. The fuse link is usually of some relatively fusible metal.

Various attempts have been made to pro vide a renewable fuse which it would be diflicult to overload. For example. renewable fuses have been madein which the passage for the fuse link was just of the proper size to take a usual flat or round fuse link of predetermined current-carrying capacity. Since the usual fuse links are of relatively fusible material, such fuses could be readily overloaded by substituting for the fuse link of predetermined current-carrying capacity a fuse link of relatively lesser fusibility, so that currents in excess of those intended to be carried would flow through the fuse to the consequent detriment of the electrical devices supplied with current.

Renewable fuses as above described have not met with complete success, for the reason that it was possible for the operative in the shop to readily overload the fuse by proper selection and substitution of a fuse strip of greater current carrying capacity than the one intended to be used. and many of the rigid inspection services have not approved such renewable fuses for general use.

It is an object of my invention, therefore, to obviate, to a large extent, the difficulties above indicated and to provide a renewable fuse which it will be difficult or practically impossible for the shop operative to overload.

Other minor objects and features of inven tion will appear as the specification proceeds.

In the preferred form of my invention I employ a suitable fuse body having a passage for a fuse link. Some part of the passage is of predeterminedirregular shape, that is, a shape which will not receive the usual flat or round type of fuse link or strip of metal of a size sufiicient to overload the fuse. My improved fuse link has at least a part thereof of a predetermined sliap'e corresponding substantially to the shape ofthe irregular portion of the passage, in the fuse body. Suitable means areprovided for making proper contact with the fuse link at the ends of the fuse body and connecting the ly in the plane of the line 33 of Fig, l,

but showing parts of the fuse in the position occupied when the fuse has been blown:

4 is a detail view of one ofthe baffles shown in Fig. 1;

Fig. 5 is a similar view of an end cap;

Fig. 6 is a view similar to Fig. 4, but viewed from the other side;

'Fig; 7 is a detailvview of the other end cap of the fuse; and

Fig. 8 is a fragmentary detail sectional View. In the form shown, 8 indicates the main body of the fuse, which is preferably of insulating material. 9, 10 indicate end caps, suitably secured to the end of the body 8, as by means of screw threads. ll, 12 indicate covercaps which, in the form shown, are threaded onto the caps 9, 10. The end caps 11, 12 are usually received in suitable. clips on the fuse board (not shown), and these caps or ferrules constitute only one of the means usually employed for connecting the fuse in the circuit. The end cap 10 has a passage 13 therethrougn and, as illustrated, is of consider ably larger sizethan the fuse link 14 which passes therethrough. The end cap9 is pro vided with a passage 15, which is preferably of irregular shape. In the specific form illustrated, this passage has facing projections and depressions extending longitudinally of the fuse, so as to give the appear ance in cross section of being corrugated.

The fuselink 14 herein shown has at least a portion thereof of a shape corresponding substantially to that of the irregularshaped opening in the cap,

reduced cross section.

block and a movable block 21.

so that the fuse link may be passed through the irregular opening. The fuse link shown is provided with one or more depressions 16 and ribs 17 so that the fuse link may be said to be transversely corrugated. One portion of the link may be a plain, flat strip 18, and between the two ends the crosssection ispreferably reduced, as at 19, so that the link in fusing will break at the intermediate portion of An additional irregular opening for the passage of the link may, if desired, be provided within the body of the tube. Such a passage may be provided for in a partition member, which preferably comprises a fixed Interposed between the two blocks may be a spring 22 for urging the movable block upwardly, as viewed in Figs. 1 and 3. The fixed block in the form shown serves as a guide for the movable block. One or both of these blocks is provided with a passage for the fuse link, and at least one of these passages is preferably of the irregular shape, to take the fuse link of corresponding shape. The movable block is provided with a stem 23, visible and operable from theoutside of the fuse body, andbetween the fuse body and the head on the stem there may be provided a spring 2 1, for urging the block up wardly. The stem passes through an aperture 25 in the fuse body, and when the block 21 is in its uppermost position a part thereof preferably engages the inside of the fuse body, to seal the opening 25 and prevent flame caused by blowing of the fuse from issuing therefrom.

Between the caps on each end of the fuse body baffle members 26, 27 may be mounted. These bames are slightly spaced from the cover caps, as indicated at 28, 28, and apertures 29, 29 in the cover caps overstand the battles. between the two caps at each end of the fuse and preferably between the baffles and the end caps. It is desirable to form a tortuous path for the escape of gases generated in the fuse when the latter is blown, and the baffles above described provide such apassage. 'In order to prevent the bafiies from becoming lost or deliberately removed the latter are pivoted to the caps, as by means of pins 30. These pins preferably extend into the body 8, as indicated in Fig. 8, and assist in holding the end caps to the body. As a precautionary measure the lengthof the fuse link and the caps may be so proportioned that if the baffles are deliberatel -J removed a proper contact will not beformed. I

I The end cap 9 in the form shown is pro vided with a seat or plateau '32, to receive the'irre ular-shaped end of the fuse link. The-"bae 26 may be provided with a seat The ends of the fuse link are held (not shown), indicating the current-carry.

ing capacity of the fuse. Both end caps may be provided with apertures 35, 35 for the escape of gases generated when the fuse is blown.

When a fuse link is to be inserted in the I fuse body the knob 23 is depressed, to cause the aperture in the movable block to move to a point near the center of the body. The fuse link 1 1 is then inserted through the aperture 13, then through the aperture. in one or both blocks (one of which is preferably of the irregular shape to receive the fuse link). The end of the fuse link is then passed through the aperture in the other head which, in the form shown, is of the irregular shape, to receive the correspondingly shaped fuse link.

The bafiies 26, 27 which, during insertion of the link were swung on their pivots to an out-of-the-way position, are then swung back and make contact with the link. The cover caps are then screwed on and the fuse is complete. The indicating end of the stem 23 is in depressed position indicating that the fuse is set.

WVhen the fuse is subjected to an abnormally high current the link will be fused and, if constructed with an intermediate portion of reduced cross section, will fuse between its ends andthe movable block 21 will be elevated and the upper edge of the block 21 will close the aperture 25, and the knob 23 projecting upwardly will indicate to an observer that the fuse has been blown. The gases generated within the fuse body will escape by the tortuous paths above de scribed, and any flame will be dissipated before reaching the exterior of the fuse.

In fuses it sometimes happens that the fuse link, in melting, will solder the cover cap fast to the end cap, and when it is attempted to unscrew the cover cap from the end cap the end and cover caps move as a unit and the end cap is unscrewed from the body, instead of as intended. I have. therefore, shown in Fig. 1 an end cap and body provided with a left-hand thread 36, while the exterior of the end cap and the interior of the cover cap are provided with a righthand thread 37. It will therefore be-obvious that when the cover cap is unscrewed, the end cap will be screwed into tighter engagement with the body. Of course, when the cover cap is screwed down after filling the fuse the tendency is to unscrew the end cap from the body, but no difficulty will be eX- perienced, for the reason that the force required' for screwing the cover cap on is relatively slight compared with the force required to unscrewthe cover cap if the same has been soldered fast.

Vith a fuse body having a passage of irregular shape, it will be obvious that a strip of metal of a size to carry sufficient current to overload the fuse cannot be inserted unless the strip be made to conform in shape to the irregularpassage. 3 e itis rather ditiicult to form a strip into the required irregular shape without special tools there will be little likelihood of a person deliberately forming a stripof metal of high current carrying capacity and inserting the same so as to overload the fuse.

It is to be observed that various features of the invention may be used in other connections than that shown. No attempt has been made to illustrate the various irregular shapes of link and corresponding passage which will accomplish the purpose herein disclosed. I believe the idea of a fuselink of irregular shape and a fuse having a passage substantially conforming in shape to be broadly new, and I therefore wish it understood that many modifications may be made under the following claims.

I claim:

1. In a renewable fuse, aninsulating body member having end caps thereon, an intermediate partition member within said tube, one of said members having an open ng of irregular cross-section, a fuse link engaging said end caps and passing through said opening of irregular crosssection, a part of said fuse link being of a cross-section substantially conforming in shape to the crosssection of said irregular shaped opening, the irregular shaped part of said link extending through and a substantial distance beyond the opening of irregular section.

2. In a renewable fuse, a cylinder of insulating material, end caps thereon, an intermediate partition member, one of said members having a corrugated opening therethrough and a fuse link passing through said insulating tube and passing through said corrugated opening, a part of said link being of such cross sectional shape as to pass through said corrugated opening, said last mentioned part of said link passing through and extending a substantial distance beyond said corrugated opening.

3. In a fuse, an insulating tube, end caps on said tube and having passages therethrough for a fuse link, cover caps for said tube, a fuse link passing through said tube and through the passages in said end caps, the passage in one of said end caps being of predetermined irregular shape and a part of said fuse link being of corresponding irregular shape to fit said passage of irregular shape.

4. In a fuse, an insulating tube, an end member at one end of said tube and having a passage of predetermined irregular shape for a fuse link of corresponding shape, a fuse link extending through said tube and through and beyond said passage, and cover caps for said tube and securing the ends of said fuse link.

5. In a fuse, an insulating tube, end members for said tube, at least one of said end members having a passage of predetermined irregular shape for a fuse link of corre sponding irregular shape, cover caps for said tube, a fuse link extending through said tube and through said passage of irregular shape and extending outside of and over said end members and being secured thereon by said cover caps.

6. In a fuse, an insulating tube, end members for said tube, at least one of said end members having a passage of predetermined irregular shape for a fuse link of corresponding irregular shape, cover caps for said tube, a fuse link extending through said tube and through said passage of irregular shape and extending outside of and i said and members and being secured thereon by said cover caps, and a movable indicator member in said tube and removed from the ends thereof and held in one position by said fuse link, and means for moving said indicator to a different position when the fuse link is ruptured.

7. As an article of manufacture, a unitary fuse link formed of a single piece of fusible sheet metal and having a portion intermediate the ends of reduced cross section, one end being flat and the other end being of predetermined irregular transverse cross .ection forming longitudinal corrugations extending to said intermediate reduced por tion, at least a part of said portion of re duced cross section being of predetermined irregular transverse cross section.

8. As an article of manufacture, a fuse link, one end of which is of flat cross-section, and the other end of which is provided with alternate ridges and channels extending substantially longitudinally thereof and extending to substantially the center thereof.

v9. As an article of manufacture, a fuse link having portion intermediate its ends of reduced cross-section, a portion of said link being provided with alternate ridges and channels extending longitudinally thereof, at least one of which extends to and at least part way along said section of reduced cross-section.

10. In a fuse, a body having a passage therethrough for a fuse link, a part of said passage being of predetermined irregular cross-section, and a fuse link having a part of substantially corresponding irregular cross section and secured in said body, the irregular section part of said link extending through and a substantial distance beyond said passage of irregular cross secformed to fit said part of said passage and extending therethrough and a substantial distance beyond said part of said passage. 12. In a fuse, a fuse body having a passage through one end thereof, a fuse link extending through and beyond said passage, said passage and a part of said fuse link being of irregular shape and corresponding to each other in shape. 7

13. In a fuse, a tube having at least one end cap thereon, a cover cap for the end of said tube, a fuse link extending through said tube and abutting at least one of said cap members, the cap member which abuts said link having an irregular surface for engaging the link.

14. As an article of manufacture, a fuse body having a longitudinal passage for a fuse a art of said assa 'e bein of aredetermined irregular shape and of fixed pre determined size for receiving a fuse link of corresponding size and shape. 7

15. 111 a fuse, a tube having a fuse link extending therethrough,end caps for said tube having passages for said link, cover caps'for said tube, an intermediate baffle for each end of said tube and lying between the caps on each end of said tube, andeach secured to one of the caps, said link being held by and between said caps at each end oft-he fuse and said cover caps having apertures therethrough and extending over said baffies.

16. In a fuse, a fuse body, means for securing a fuse link at the ends of the body, a partition member in said fuse body and independent of said means, said partition member 11 ving a passage therethrough for a fuse link, said passage and a part of said fuse link beingofirregular shapeand corresponding toeach other in shape.

17. In a fuse, a fuse body, means for. securing a fuse link at the e-nds'of the body, a partition member in and removed from the ends of said fuse body and including fixed and movable blocks, at least one of said blocks having a passage therethrough for a fuse link, said passage and a part of said fuse link being of irregular shape and corresponding to each other in shape] 18. In a fuse, a fuse body, means for securing a fuse link at the endsv of the body,

a partition member in and removed from the ends of said fuse body and including fixed and movable blocks, said blocks having passage therethrough for a fuse link, one of said passages and said fuse link being of irregular shape and corresponding to each other in shape. I

19. In a fuse, a fuse body, means for securing a fuse link at the endsof the body, a movable block in and removed from the ends of said fuse body, said block having a passage therethrough for a fuse link, said passage and a part of said fuse link being of irregular shape and corresponding to each other in shape, said movable block having a part visible from the outside of the body and acting as an indicator.

20. In a fuse, an insulating tube having an end cap thereon, cover caps for the ends of said tube, an intermediate baffle between the end cap and one cover cap of said tube, a pin for pivoting said baflie to said end cap, said pin extending into said insulating tube for preventing rotation between the lat ter and said end cap.

'21. In a fuse, an insulating tube, an end cap secured to said tube by means of a left hand thread, a cover cap secured over said end cap by meansof a righthand thread, whereby when the cover capis unscrewed,

- the end cap will be forced into tigliter.en

gagement With said tube.

GEORGE a. TRUMBULL. 

